I concur, all of the other dinosaurs from the previous game have been added and icons for the three hybrids have been found in JWE2's files, so therefore they should add them via a free update.
Additional hybrids are an extremely controversial idea on the forums, so this may not get the best reception from other users. I would personally love to see the ones from JWE1 back at the very least!
I'm not a fan of the hybrids, but if it is part of JW cannon, for example Scorpios rex, then go for it. I just want the focus to be on actual paleontological creatures, even if the depictions of them are not paleontologically accurate.